1. Field of the Invention
The present invention relates to a scroll type compressor, particularly to an improvement of the sealability for a beginning area of a spiral body in a movable scroll member and an improvement of a discharging port of a stationary scroll member in the compressor.
2. Description of the Related Arts
As shown in FIG. 6, the conventional scroll type compressor comprises a stationary scroll member 52 fixed in a housing 51, and a movable scroll member 53 rotatably accommodated in the housing 51. The stationary scroll 52 member consists of a stationary side plate 21 and a stationary spiral body 22 comprising outer and inner walls defined, respectively, by an involute curve or other and integrally fixed on one surface of the stationary side plate 21. The movable scroll member 53 consists of a movable side plate 31 and a movable spiral body 32 comprising outer and inner walls defined, respectively, by an involute curve or other and integrally fixed on one surface of the side plate 31, both spiral bodies 22 and 32 being engaged with each other with a phase difference of 180.degree. therebetween. Grooves 22a and 32a are formed, respectively, along ridges of the stationary and movable spiral bodies 22 and 32 extending the spiral direction thereof. As shown in the enlarged view of seal 32b in FIG. 7, tip seal elements 22b and 32b, shown in FIG. 6, are accommodated in the grooves 22a, 32a, respectively, for sealing the gap between the spiral bodies 22, 32 and the side plates 31, 21.
As shown in FIG. 6, the rotation of a drive shaft 54 is converted to an orbital motion of the movable scroll member 53 through an eccentric bush 57 and an anti-spin mechanism 58. The structures and functions of the eccentric bush and the anti-spin mechanism are described in detail in, for example, Japanese Unexamined Patent Publication (Kokai) No. 57-148087 or 57-148092. According to the orbital motion of the movable scroll member 53, a volume of a compression chamber 55 formed between the scroll members 52, 53 is gradually decreased while the compression chamber 55 is displaced to a central area of the scroll members, whereby a fluid in the compression chamber 55 is compressed and finally discharged therefrom through a discharging port 61 of the stationary side plate 21, into a discharging chamber 60. At this stage, the tip seal element 32b is pressurized from the back by a coolant gas from a high pressure side HP positioned closer to the center of the stationary side plate 21, whereby the tip seal element 32 is brought into tight contact with a wall of the groove 32a adjacent to the low pressure side LP positioned farther from the center of the stationary side plate 21, and brought into tight contact with a surface of the stationary side plate 21 via a film of lubricant contained in the coolant gas, so that the coolant gas is sealed in the compression chamber 55. The tip seal element 22b functions in a similar manner.
In the conventional compressor, the tip seal element 32b is not provided in the beginning area, i.e., the radially inner extremity, of the movable spiral body 32. This is because, as shown in FIG. 8, the discharging port 61 of the conventional compressor has a circular shape, and if the tip seal element 32b were located in this area, the tip seal element 32b would be liable to be sucked from the groove 32a into the discharging port 61 when the tip seal element 32b overlapped the discharging port 61 in the course of the orbital motion of the movable scroll member 53, whereby the tip seal element 32b would be damaged by the edge of the latter. Accordingly, the conventional compressor has a drawback of an incomplete sealability at the beginning area of the movable spiral body, and as this area is subjected to the maximum pressure during the compression process, a pressure loss is liable to occur.